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Welding anodized aluminum

04-02-2007, 09:24 AM

Anybody with any experience welding anodized aluminum? I have welded lots of aluminum things but never anodized. Some that I have looked at looks like the weld is painted with something. What do they "paint" it with. Almost looks like primer but I'm sure thats not what its, it matches the anodized aluminum pretty well. Also, any info on the welding process would be helpfull.

Hey HMW,
Been welding aluminum many years now. Anodizing is simply an electrolytic process that adds a protective coating to the aluminum. To get the best welds, the anodizing should be removed with a flap sanding disc (40-60grit) on the welded areas. 4043 will give the closest color match and 5356 is close. The alum. then can be re-anodized, if necessary, or if cost-prohibitive, coated with a clear acrylic coating....Denny

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The problem with 4043 as I understand, is if you "re anodize", it will turn black. I have not personally done this, but have read this in many sources. I would imagine you need to increase the positive side of the wave for better cleaning action to remove the oxide coating better. Hope this helps, Pual

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Yes, i've been told that 5053 is best if you are going to anodize it. What I have seen is towers that already are anodized and have been welded. I guess you can bend the stuff with out the anoidizing cracking. The welds were definatley made after it was anodized. Maybe it is a clear paint on the welds, it looks good. Also I have read you dont need to clean off the anodized, but can weld right through it. Also read about using a on/off switch on the torch for this process. I have a foot pedal now and have seen thumb controls but not and on/off switch. I see I'm going to have to find some scrap to play with. I recently extended the pedestals on 2 boat seats. I had to sit in teh floor of the boat with the pedal under my leg, worked Ok but thumb controls might be easier I dont believe they were anodized as it welded pretty easy. Maybe a clear coat like wheels or something but not much. I painted the weld with "aluminum" colored rustoleum paint and looks pretty good. of course they are under the seat so you really cant see them very well, but still didn't want the weld to corrode. The tower in this boat is awesome looking.

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Here is a couple of pics of the Tee top. The welds are very nice, but i would like to know what they painted over the weld with. Looks nice. sorta gray in color. The seat pictures are where i raised the pedastels 5". Kinda hard since the aluminum pedastel has grooves all the way around and they could not be removed from the boat. Also it seemed like they were clear coated, sorta like a wheel, so when I cleaned off the area to weld you could tell the clear coat was removed. Owner was happy with new "higher" seats. Talked over with owner and he agreed to just paint over clear coat removed area with "aluminum colored" rustoleum paint

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Trigger switches are great for out of possition welding but you bassicly have to forget about having that on demand control of your amperage. It's a bit awkward at first but easy to get used to if you have GTAW experience. Out of 50 - 100+ GTAW machines at work we have only 3 - 4 foot pedals since almost every thing is out of possition. By the way great work.
Hope this answers your question about trigger switches.

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Thanks for the thoughts. I think when i get my next T.I.G I'm going to get the thumb wheel. All of my work so far has been with the pedal and its been Ok. Alot of bench work. But lately it seems the hand control would be better, just have to used to using it I guess.

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When welding anodized aluminum, t-Tops,etc.which are too large(and expensive) to re-anodize after fabrication, the anodizing is not grinded off before welding. The welds or painted, hand brush or airbrush with an aluminum color paint found at most hardware stores. Most use the tig process with the high freq. switch on start and use a button type switch mounted to the torch. The switch will close when depressed and the arc should jump to the weld and open when you let off to stop the arc. The process is to create an arc and fill the puddle, stop to allow the puddle to solidify, then move the cup 1/8"- 1/4" and restart the arc. This will produce the "stack of dimes" look. This is one of the most difficult materials to weld due to the anodized coating which makes for a trashy weld.Those who have mastered the technique learn to "throw the trash" to one side of the cap while the largest remaing part of the cap is a shiny silver color. Either way the weld is painted to stop corrosion on the now unprotected metal. I believe the newest techniques use an inverter where the above process probably changes and causes the stack of dimes look to be closer together. I have not tried this new machine, probably a Miller Dynasty, but others who have might comment on this. I think Engloid welds ski arches from anodized. Maybe they use the inverters.

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I am around a lot of marine stuff too (both in factories and in the repair segment)... but what I see is not painted afterward. The weld just takes on a frosty sorta look. I seen some people try it in the nineties with little success. Mainly pontoon railings etc.
Cracker(Jack) are you seeing people (pro's) actually paint their welds?? On BDA?

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On pontoon boats, almost all parts are usually fabricated in flat sections and then anodized. The parts are then bolted together in sections. Unlike the tee tops and tuna towers, which are all welded construction and too large to anodize afterwards, especially since they are now three dimensional. The anodizing process is similar to chrome plating which requires an acid tank for the process. Unless your tank is large enough, you are limited to size. Now they can be rotated in the tank but this is usually too costly. It is hard enough to get customers to pay for custom work with the welds being painted. Yes, I have seen and done this professionally and what I have witnessed is done this way. If you take a tee top, try some paint remover on the welds and you will see the paint come off. Look at pic #1, this was definitely painted with a brush.Oh, BDA? Not sure what you mean, refresh my memory.